Develop Reference

check numeric value of a datagrdiview cell value?

In my project, I have a datagridview with some columns, one of the columns have a numeric value. I want to perform a check for this cell value but it gives me an error
string was not in a correct value.
this is my code:
foreach (DataGridViewRow rw in dgv_student_update.Rows)
{
for (int i = 0; i < dgv_student_update.Rows.Count; i++)
{
if (Convert.ToInt32(rw.Cells[3].Value) == 4)
{
sc.archive_student(dgv_student_update.Rows[i].Cells[2].Value.ToString(),last_year + " - " + current_year,Convert.ToInt32(dgv_student_update.Rows[i].Cells[1].value));
}
}
}
can anyone help please?

Try this
Func<DataGridViewRow, int, int> cellValue = (row, i) => {
int.TryParse(row.Cells[i].Value + "", out i); return i; }; // returns 0 if TryParse fails
foreach (DataGridViewRow rw in dgv_student_update.Rows)
if (cellValue(rw, 3) == 4)
sc.archive_student(rw.Cells[2].Value.ToString(),
last_year + " - " + current_year, cellValue(rw, 1));

It's just a matter of proper null and value checking. You cannot assume everything has a value and it is in the format you expect. First make sure the cell has a value. Then make sure the value can be converted to an integer. Follow this advice for your update as well, you are likely to hit the same kind of problem calling archive_student.
for (int i = 0; i < dgv_student_update.Rows.Count; i++)
{
if(rw.Cells[3].Value != null)
{
string strCell3 = rw.Cells[3].Value.ToString();
int intCell3 = 0;
if(int.TryParse(strCell3, out intCell3))
{
if (intCell3 == 4)
{
sc.archive_student(dgv_student_update.Rows[i].Cells[2].Value.ToString(),last_year + " - " + current_year,Convert.ToInt32(dgv_student_update.Rows[i].Cells[1].value));
}
}
else
{
//you decide what to do if its not an integer value
}
}
else
{
//you decide what to do if cell has no value
}
}

Computation of final grades in a listview

This is all of the code i have done so far. The system has a listview that has a column header:
subject name | 1st | 2nd | 3rd | 4th | Final Grades
If the column 1st to 4th contains value it will compute for the final grade of the student. sum(1st to 4th) / 4 *50 + 50. if one of the column does not have a value then the user will be prompted and no final grades will be computed.
I am confused on how do i get all the listview value from 1st to 4th then automatically computes the final grade.
PLease help
private void button1_Click(object sender, EventArgs e)
{
flag = false;
if (txt_numValue.Text != "")
{
char[] entereddata = txt_numValue.Text.ToCharArray();
foreach (char aChar in entereddata.AsEnumerable())
{
if (!Char.IsDigit(aChar))
{
MessageBox.Show("Please enter only numbers.", "In the field Numeric Value");
flag = true;
break;
}
}
}
else if (txt_numValue.Text == "")
{
MessageBox.Show("Please do not leave the field, 'Numeric Value', blank.", "Attention!");
flag = true;
}
if (flag == false)
{
string period = txt_gradingPeriod.Text;
string numeric = txt_numValue.Text;
int cell = 0;
if (period == "1st") { cell = 1; }
else if (period == "2nd") { cell = 2; }
else if (period == "3rd") { cell = 3; }
else if (period == "4th") { cell = 4; }
foreach (ColumnHeader header in listView1.Columns)
{
if (header.Text == period)
{
listView1.Items[0].SubItems[cell].Text = numeric;
break;
}
}
}
}

Once you have got all the data in your list view you can do something like this,
int sum = 0;
foreach (ListViewItem v in listView1.Items)
{
bool hasBlank = false;
for (int i = 0; i < v.SubItems.Count;i++ )
{
if (v.SubItems[i].Text == null || v.SubItems[i].Text == string.Empty)
{
//code
hasBlank = true;
break;
}
else
{
sum += Convert.ToInt16(v.SubItems[i].Text);
}
}
if (!hasBlank)
{
string grade="something";
//formula to calculate grade based on sum.set the result to string grade
v.SubItems[4].Text = grade;
}
else
{
v.SubItems[4].Text = "has blank";
}
sum = 0;
}
This will fill grade if all values are present else a message that it has a blank value.

Adding elements of a list c#

Guys I have a query that returns 3 values (-4.00 , -7.53 , -15.00.
I am returning these in list named ReaderResult as shown in codes,however while they are added to the list I also want to keep the total of the elements being added in the list
DataReader = DoQuery(" select oa.[OtherAmount] FROM [Biatss_PC_SRV].[Pax].[SalesDocumentOtherAmount] as oa "
+"INNER JOIN [Biatss_PC_SRV].[Pax].[SalesRelatedDocumentInformation] as rd on oa.RelatedDocumentGuid = rd.RelatedDocumentGuid "
+"INNER JOIN [Biatss_PC_SRV].[Pax].[SalesDocumentHeader] as h on rd.HdrGuid = h.HdrGuid where h.DocumentNumber = '" + txtTicketNumber.Text.ToString() + "'");
//check DataReader
if (DataReader == null)
{
DataReader.Close();
DataReader.Dispose();
}
else
{
if (DataReader.HasRows)
{
//setting variables to be used to initial values
ii = 0;
double sumOfTaxes = 0;
ReaderResult.Clear();
while (DataReader.Read())
{
//for ( ii = 0; ii < DataReader.FieldCount; ii++)
//{
if (DataReader.IsDBNull(0))
{
string CaseNull = "";
ReaderResult.Add(CaseNull);
}
else
{
//put results in LIST<>
ReaderResult.Add(Convert.ToString(DataReader.GetDecimal(0)));
//double sumLaSa =+ Convert.ToDouble(ReaderResult.Last()); VALUE HERE IS ONLY THE LAST OF THE 3 NOT THE SUM
//sumOfTaxes =+ Convert.ToDouble(DataReader.GetDecimal(0));
//double sumLaSa =+ Convert.ToDouble(ReaderResult.Last().Last()); ERROR I GET HERE says cannont convert char to double
myTextboxListForAmounts[ii].Text = Convert.ToString(DataReader.GetDecimal(0));
// }
if (ii > 6)
{
//make txtXT visible and display summed up amount in it
lblXT.Visible = true;
txtXT.Visible = true;
txtXT.Text = Convert.ToString(sumOfTaxes);
}
ii++;
}
}
}
else
{
DataReader.Close();
DataReader.Dispose();
}
DataReader.Close();
DataReader.Dispose();
}
How can I get the sum of the values returned please ?

Solved the problem.
The aim is reached using the solution ignited by Corak.
sumOfTaxes =+ Convert.ToDouble(DataReader.GetDecimal(0));
modified to
sumOfTaxes += Convert.ToDouble(DataReader.GetDecimal(0)); (+= instead of =+)
enter code here

Mixed managed C++ method does not always return the same result to the calling C# code

A C++ method returns the correct value when I use a conditional breakpoint, but an incorrect value without a breakpoint.
C# method which calls C++:
bool SetProperty(Element element, Node referencePoint, List<Materializer> materializers, List<ulong> properties)
{
// Loop over STLs
for (int i = 0; i < materializers.Count; i++)
{
Materializer materializer = materializers[i];
if (materializer.IsPointInside(referencePoint.X, referencePoint.Y, referencePoint.Z, pentalTreeDatasets[i].top))
{
element.PropertyId = properties[i];
return true;
};
}
return false;
}
C++ methods in the header file:
int CountIntersects(double x, double y, double z, PentalTreeNode ^root)
{
Math3d::M3d rayPoints[2], intersectionPoint;
rayPoints[0].set(x,y,z);
rayPoints[1].set(x,y,1.0e6);
if(!root)
return 0;
else
{
int special = CountIntersects(x,y,z,root->special);
if (x <= root->xMax && x >= root->xMin && y <= root->yMax && y >= root->yMin)
{
if( _stlMesh->IsRayIntersectsPoly(root->index, rayPoints, intersectionPoint))
{
return (1 + special);
}
else
return special;
}
else
{
if (y>root->yMax)
{
return (CountIntersects(x,y,z,root->top)+special);
}
else if(y<root->yMin)
{
return (CountIntersects(x,y,z,root->bottom)+special);
}
else if(x<root->xMin)
{
return (CountIntersects(x,y,z,root->left)+special);
}
else if(x>root->xMax)
{
return (CountIntersects(x,y,z,root->right)+special);
}
else
return special;
}
}
}
bool IsPointInside(double x, double y, double z, PentalTreeNode ^root)
{
int intersectionCount = 0;
Math3d::M3d rayPoints[2], intersectionPoint;
rayPoints[0].set(x,y,z);
rayPoints[1].set(x,y,1.0e6);
if(_box->IsContainingPoint(x,y,z))
{
intersectionCount=CountIntersects(x,y,z,root);
return (intersectionCount%2!=0);
}
}
C++ methods in other header files:
bool IsRayIntersectsPoly(int nPolygonIndex, Math3d::M3d RayPoints[2], CVector3D& IntersectionPoint)
{
CMeshPolygonBase& Poly = m_PolygonArray[nPolygonIndex];
CArrayResultI Result;
int* pPolygonPoints = GetPolygonPoints(Poly, Result);
Math3d::MPlane TrianglePlane;
double Atmp[3], A;
CVector3D* pPoints[3];
pPoints[0] = &m_PointArray[*pPolygonPoints].m_Position;
for(int i = 1; i < Result.GetSize() - 1; i++)
{
pPoints[1] = &m_PointArray[*(pPolygonPoints+i)].m_Position;
pPoints[2] = &m_PointArray[*(pPolygonPoints+i+1)].m_Position;
TrianglePlane.Init(*pPoints[0], *pPoints[1], *pPoints[2]);
TrianglePlane.IntersectLine(RayPoints[0], RayPoints[1], IntersectionPoint);
A = GetTriangleArea(*pPoints[0], *pPoints[1], *pPoints[2]);
for(int j = 0; j < 3; j++)
{
Atmp[j] = GetTriangleArea(*pPoints[j], *pPoints[(j+1)%3], IntersectionPoint);
}
if( fabs(A - Atmp[0] - Atmp[1] - Atmp[2]) < 1.0e-5 ) return true;
}
return false;
};
double GetTriangleArea(CVector3D& T1, CVector3D& T2, CVector3D& T3)
{
double a, b, c, s;
a = (T1 - T2).length();
b = (T2 - T3).length();
c = (T3 - T1).length();
s = 0.5 * (a + b + c);
return( sqrt(s * (s - a)* (s - b)* (s - c)) );
}
When I start the program which calls SetProperty() within the for-loop, the results for some iterator values are wrong. When I set conditional breakpoints for critical iterator values in the for-loop and step over it, then the result is OK for that item. What may be the problem?
This is method in which I post breakpoint. For example, for critical element.Id==2393.
private void StartButton_Click(object sender, EventArgs e)
{
DateTime startTime = DateTime.Now;
List<Materializer> materializers = new List<Materializer>();
List<ulong> properties = new List<ulong>();
// Load STLs
for (int i = 0; (int)i < (this.dataGridView.RowCount - 1); i++)
{
if (dataGridView.Rows[i].Cells[1].Value != null && (string)dataGridView.Rows[i].Cells[1].Value != "")
{
Materializer materializer = new Materializer();
materializer.LoadSTLMesh(dataGridView.Rows[i].Cells[0].Value.ToString());
materializers.Add(materializer);
properties.Add((ulong)dataGridView.Rows[i].Cells[1].Tag);
}
}
CreatePentalTrees(materializers);
int processedElementCount = 0;
int changedElementCount = 0;
// Loop over elements
foreach (Element element in model.ElementsList.Values)
if ((element.Topology == 7 || element.Topology == 8) && !lockedProperties.ContainsKey(element.PropertyId)) // 3D elements only
{
Node center = this.CenterPoint(element, model.NodesList);
if (element.Id == 2393)
{
//if breakpoints thats ok, else not ok
Console.WriteLine(element.Id);
Console.WriteLine(element.PropertyId);
}
if (SetProperty(element, center, materializers, properties)) // Check for center point
{
//changedElements.Add(element.Id, true);
changedElementCount++;
}
else
{
// Check for all nodes if center point does not belong to any STL
int[] nodeOrder;
switch (element.Topology)
{
case 7:
nodeOrder = wedgeNodeOrder;
break;
case 8:
nodeOrder = brickNodeOrder;
break;
default:
throw new Exception("Unknown topology " + element.Topology.ToString());
}
for (int i = 0; i < nodeOrder.Length; i++)
{
Node node = model.NodesList[element.NodeIds[nodeOrder[i]]];
if (SetProperty(element, node, materializers, properties))
{
//changedElements.Add(element.Id, true);
changedElementCount++;
break;
}
}
}
if (++processedElementCount % 100 == 0)
{
labelTime.Text = "Changed/processed elements: " + changedElementCount.ToString() + "/" + processedElementCount.ToString();
labelTime.Refresh();
Application.DoEvents();
}
}
DateTime endTime = DateTime.Now;
labelTime.Text = "Total time: " + (endTime - startTime).TotalSeconds.ToString() + " s";
MessageBox.Show("Completed.");
SaveFileDialog saveFileDlg = new SaveFileDialog();
saveFileDlg.Title = "Save FEMAP neutral file";
saveFileDlg.Filter = "(*.neu)|*.neu";
if (saveFileDlg.ShowDialog() == System.Windows.Forms.DialogResult.OK)
{
FemapNeutral.ExportNeu(saveFileDlg.FileName, model);
}
}

You seem to be calling a lot of methods you haven't listed, and/or the wall of code made me get lost. Adding that code won't help: reducing your problem to a simpler one that demonstrates the problem might.
However, the most likely cause of your problem, if you have unmanaged code reading managed data, is that you failed to marshal or pin the data prior to using the managed code.
Unpinned data can be moved around by the garbage collector in unexpected ways.

Evaluating string "3*(4+2)" yield int 18 [duplicate]

This question already has answers here:
Is it possible to compile and execute new code at runtime in .NET?
(15 answers)
Closed 9 years ago.
Is there a function the .NET framework that can evaluate a numeric expression contained in a string and return the result? F.e.:
string mystring = "3*(2+4)";
int result = EvaluateExpression(mystring);
Console.Writeln(result); // Outputs 18
Is there a standard framework function that you can replace my EvaluateExpression method with?

If you want to evaluate a string expression use the below code snippet.
using System.Data;
DataTable dt = new DataTable();
var v = dt.Compute("3 * (2+4)","");

Using the compiler to do implies memory leaks as the generated assemblies are loaded and never released. It's also less performant than using a real expression interpreter. For this purpose you can use Ncalc which is an open-source framework with this solely intent. You can also define your own variables and custom functions if the ones already included aren't enough.
Example:
Expression e = new Expression("2 + 3 * 5");
Debug.Assert(17 == e.Evaluate());

Try this:
static double Evaluate(string expression) {
var loDataTable = new DataTable();
var loDataColumn = new DataColumn("Eval", typeof (double), expression);
loDataTable.Columns.Add(loDataColumn);
loDataTable.Rows.Add(0);
return (double) (loDataTable.Rows[0]["Eval"]);
}

You could look at "XpathNavigator.Evaluate" I have used this to process mathematical expressions for my GridView and it works fine for me.
Here is the code I used for my program:
public static double Evaluate(string expression)
{
return (double)new System.Xml.XPath.XPathDocument
(new StringReader("<r/>")).CreateNavigator().Evaluate
(string.Format("number({0})", new
System.Text.RegularExpressions.Regex(#"([\+\-\*])")
.Replace(expression, " ${1} ")
.Replace("/", " div ")
.Replace("%", " mod ")));
}

This is a simple Expression Evaluator using Stacks
public class MathEvaluator
{
public static void Run()
{
Eval("(1+2)");
Eval("5*4/2");
Eval("((3+5)-6)");
}
public static void Eval(string input)
{
var ans = Evaluate(input);
Console.WriteLine(input + " = " + ans);
}
public static double Evaluate(String input)
{
String expr = "(" + input + ")";
Stack<String> ops = new Stack<String>();
Stack<Double> vals = new Stack<Double>();
for (int i = 0; i < expr.Length; i++)
{
String s = expr.Substring(i, 1);
if (s.Equals("(")){}
else if (s.Equals("+")) ops.Push(s);
else if (s.Equals("-")) ops.Push(s);
else if (s.Equals("*")) ops.Push(s);
else if (s.Equals("/")) ops.Push(s);
else if (s.Equals("sqrt")) ops.Push(s);
else if (s.Equals(")"))
{
int count = ops.Count;
while (count > 0)
{
String op = ops.Pop();
double v = vals.Pop();
if (op.Equals("+")) v = vals.Pop() + v;
else if (op.Equals("-")) v = vals.Pop() - v;
else if (op.Equals("*")) v = vals.Pop()*v;
else if (op.Equals("/")) v = vals.Pop()/v;
else if (op.Equals("sqrt")) v = Math.Sqrt(v);
vals.Push(v);
count--;
}
}
else vals.Push(Double.Parse(s));
}
return vals.Pop();
}
}

static double Evaluate(string expression) {
var loDataTable = new DataTable();
var loDataColumn = new DataColumn("Eval", typeof (double), expression);
loDataTable.Columns.Add(loDataColumn);
loDataTable.Rows.Add(0);
return (double) (loDataTable.Rows[0]["Eval"]);
}
Explanation of how it works:
First, we make a table in the part var loDataTable = new DataTable();, just like in a Data Base Engine (MS SQL for example).
Then, a column, with some specific parameters (var loDataColumn = new DataColumn("Eval", typeof (double), expression);).
The "Eval" parameter is the name of the column (ColumnName attribute).
typeof (double) is the type of data to be stored in the column, which is equal to put System.Type.GetType("System.Double"); instead.
expression is the string that the Evaluate method receives, and is stored in the attribute Expression of the column. This attribute is for a really specific purpose (obvious), which is that every row that's put on the column will be fullfilled with the "Expression", and it accepts practically wathever can be put in a SQL Query. Refer to http://msdn.microsoft.com/en-us/library/system.data.datacolumn.expression(v=vs.100).aspx to know what can be put in the Expression attribute, and how it's evaluated.
Then, loDataTable.Columns.Add(loDataColumn); adds the column loDataColumn to the loDataTable table.
Then, a row is added to the table with a personalized column with a Expression attribute, done via loDataTable.Rows.Add(0);. When we add this row, the cell of the column "Eval" of the table loDataTable is fullfilled automatically with its "Expression" attribute, and, if it has operators and SQL Queries, etc, it's evaluated and then stored to the cell, so, here happens the "magic", the string with operators is evaluated and stored to a cell...
Finally, just return the value stored to the cell of the column "Eval" in row 0 (it's an index, starts counting from zero), and making a conversion to a double with return (double) (loDataTable.Rows[0]["Eval"]);.
And that's all... job done!
And here a code eaiser to understand, which does the same... It's not inside a method, and it's explained too.
DataTable MyTable = new DataTable();
DataColumn MyColumn = new DataColumn();
MyColumn.ColumnName = "MyColumn";
MyColumn.Expression = "5+5/5"
MyColumn.DataType = typeof(double);
MyTable.Columns.Add(MyColumn);
DataRow MyRow = MyTable.NewRow();
MyTable.Rows.Add(MyRow);
return (double)(MyTable.Rows[0]["MyColumn"]);
First, create the table with DataTable MyTable = new DataTable();
Then, a column with DataColumn MyColumn = new DataColumn();
Next, we put a name to the column. This so we can search into it's contents when it's stored to the table. Done via MyColumn.ColumnName = "MyColumn";
Then, the Expression, here we can put a variable of type string, in this case there's a predefined string "5+5/5", which result is 6.
The type of data to be stored to the column MyColumn.DataType = typeof(double);
Add the column to the table... MyTable.Columns.Add(MyColumn);
Make a row to be inserted to the table, which copies the table structure DataRow MyRow = MyTable.NewRow();
Add the row to the table with MyTable.Rows.Add(MyRow);
And return the value of the cell in row 0 of the column MyColumn of the table MyTable with return (double)(MyTable.Rows[0]["MyColumn"]);
Lesson done!!!

This is right to left execution, so need to use proper parathesis to execute expression
// 2+(100/5)+10 = 32
//((2.5+10)/5)+2.5 = 5
// (2.5+10)/5+2.5 = 1.6666
public static double Evaluate(String expr)
{
Stack<String> stack = new Stack<String>();
string value = "";
for (int i = 0; i < expr.Length; i++)
{
String s = expr.Substring(i, 1);
char chr = s.ToCharArray()[0];
if (!char.IsDigit(chr) && chr != '.' && value != "")
{
stack.Push(value);
value = "";
}
if (s.Equals("(")) {
string innerExp = "";
i++; //Fetch Next Character
int bracketCount=0;
for (; i < expr.Length; i++)
{
s = expr.Substring(i, 1);
if (s.Equals("("))
bracketCount++;
if (s.Equals(")"))
if (bracketCount == 0)
break;
else
bracketCount--;
innerExp += s;
}
stack.Push(Evaluate(innerExp).ToString());
}
else if (s.Equals("+")) stack.Push(s);
else if (s.Equals("-")) stack.Push(s);
else if (s.Equals("*")) stack.Push(s);
else if (s.Equals("/")) stack.Push(s);
else if (s.Equals("sqrt")) stack.Push(s);
else if (s.Equals(")"))
{
}
else if (char.IsDigit(chr) || chr == '.')
{
value += s;
if (value.Split('.').Length > 2)
throw new Exception("Invalid decimal.");
if (i == (expr.Length - 1))
stack.Push(value);
}
else
throw new Exception("Invalid character.");
}
double result = 0;
while (stack.Count >= 3)
{
double right = Convert.ToDouble(stack.Pop());
string op = stack.Pop();
double left = Convert.ToDouble(stack.Pop());
if (op == "+") result = left + right;
else if (op == "+") result = left + right;
else if (op == "-") result = left - right;
else if (op == "*") result = left * right;
else if (op == "/") result = left / right;
stack.Push(result.ToString());
}
return Convert.ToDouble(stack.Pop());
}

You could fairly easily run this through the CSharpCodeProvider with suitable fluff wrapping it (a type and a method, basically). Likewise you could go through VB etc - or JavaScript, as another answer has suggested. I don't know of anything else built into the framework at this point.
I'd expect that .NET 4.0 with its support for dynamic languages may well have better capabilities on this front.

I recently needed to do this for a project and I ended up using IronPython to do it. You can declare an instance of the engine, and then pass any valid python expression and get the result. If you're just doing simple math expressions, then it would suffice. My code ended up looking similar to:
IronPython.Hosting.PythonEngine pythonEngine = new IronPython.Hosting.PythonEngine();
string expression = "3*(2+4)";
double result = pythonEngine.EvaluateAs<double>(expression);
You'd probably not want to create the engine for each expression. You also need a reference to IronPython.dll

EDIT: Realised i should really bring the addition and subtraction out seperately aswell to make it a little bit more BODMAS compliant.
Big thanks to Rajesh Jinaga for his Stack based approach. I found it really useful for my needs. The following code is a slight modification of Rajesh's method, which processes divisions first, then multiplications, then finishes up with addition and subtraction. It will also allow the use of booleans in the expressions, where true is treated as 1 and false 0. allowing the use of boolean logic in expressions.
public static double Evaluate(string expr)
{
expr = expr.ToLower();
expr = expr.Replace(" ", "");
expr = expr.Replace("true", "1");
expr = expr.Replace("false", "0");
Stack<String> stack = new Stack<String>();
string value = "";
for (int i = 0; i < expr.Length; i++)
{
String s = expr.Substring(i, 1);
// pick up any doublelogical operators first.
if (i < expr.Length - 1)
{
String op = expr.Substring(i, 2);
if (op == "<=" || op == ">=" || op == "==")
{
stack.Push(value);
value = "";
stack.Push(op);
i++;
continue;
}
}
char chr = s.ToCharArray()[0];
if (!char.IsDigit(chr) && chr != '.' && value != "")
{
stack.Push(value);
value = "";
}
if (s.Equals("("))
{
string innerExp = "";
i++; //Fetch Next Character
int bracketCount = 0;
for (; i < expr.Length; i++)
{
s = expr.Substring(i, 1);
if (s.Equals("(")) bracketCount++;
if (s.Equals(")"))
{
if (bracketCount == 0) break;
bracketCount--;
}
innerExp += s;
}
stack.Push(Evaluate(innerExp).ToString());
}
else if (s.Equals("+") ||
s.Equals("-") ||
s.Equals("*") ||
s.Equals("/") ||
s.Equals("<") ||
s.Equals(">"))
{
stack.Push(s);
}
else if (char.IsDigit(chr) || chr == '.')
{
value += s;
if (value.Split('.').Length > 2)
throw new Exception("Invalid decimal.");
if (i == (expr.Length - 1))
stack.Push(value);
}
else
{
throw new Exception("Invalid character.");
}
}
double result = 0;
List<String> list = stack.ToList<String>();
for (int i = list.Count - 2; i >= 0; i--)
{
if (list[i] == "/")
{
list[i] = (Convert.ToDouble(list[i - 1]) / Convert.ToDouble(list[i + 1])).ToString();
list.RemoveAt(i + 1);
list.RemoveAt(i - 1);
i -= 2;
}
}
for (int i = list.Count - 2; i >= 0; i--)
{
if (list[i] == "*")
{
list[i] = (Convert.ToDouble(list[i - 1]) * Convert.ToDouble(list[i + 1])).ToString();
list.RemoveAt(i + 1);
list.RemoveAt(i - 1);
i -= 2;
}
}
for (int i = list.Count - 2; i >= 0; i--)
{
if (list[i] == "+")
{
list[i] = (Convert.ToDouble(list[i - 1]) + Convert.ToDouble(list[i + 1])).ToString();
list.RemoveAt(i + 1);
list.RemoveAt(i - 1);
i -= 2;
}
}
for (int i = list.Count - 2; i >= 0; i--)
{
if (list[i] == "-")
{
list[i] = (Convert.ToDouble(list[i - 1]) - Convert.ToDouble(list[i + 1])).ToString();
list.RemoveAt(i + 1);
list.RemoveAt(i - 1);
i -= 2;
}
}
stack.Clear();
for (int i = 0; i < list.Count; i++)
{
stack.Push(list[i]);
}
while (stack.Count >= 3)
{
double right = Convert.ToDouble(stack.Pop());
string op = stack.Pop();
double left = Convert.ToDouble(stack.Pop());
if (op == "<") result = (left < right) ? 1 : 0;
else if (op == ">") result = (left > right) ? 1 : 0;
else if (op == "<=") result = (left <= right) ? 1 : 0;
else if (op == ">=") result = (left >= right) ? 1 : 0;
else if (op == "==") result = (left == right) ? 1 : 0;
stack.Push(result.ToString());
}
return Convert.ToDouble(stack.Pop());
}
I know there is likely to be a cleaner way of doing it, thought id just share the first look at it in case anyone finds it usefull.

Many thanks to Ramesh. I used a version of his simple code to pull a string out a database and use it to do boolean operations in my code.
x is a number like 1500 or 2100 or whatever.
function would be a stored evaluation like x > 1400 and x < 1600
function = relation[0].Replace("and","&&").Replace("x",x);
DataTable f_dt = new DataTable();
var f_var = f_dt.Compute(function,"");
if (bool.Parse(f_var.ToString()) { do stuff }

There is not. You will need to use some external library, or write your own parser. If you have the time to do so, I suggest to write your own parser as it is a quite interesting project. Otherwise you will need to use something like bcParser.

Short answer: I don't think so. C# .Net is compiled (to bytecode) and can't evaluate strings at runtime, as far as I know. JScript .Net can, however; but I would still advise you to code a parser and stack-based evaluator yourself.