Develop Reference

Cannot find column '0' C#

I have the following piece of code.
dt3 = new System.Data.DataTable();
foreach (DataRow sourceRow in dt2.Rows) {
DataRow destRow = dt3.NewRow();
destRow[0] = sourceRow[2];
dt3.Rows.Add(destRow);
}
And it is generating following error on line destRow[0] = sourceRow[2];
System.IndexOutOfRangeException: Cannot find column 0.
What am I doing wrong? Is there any way around it without declaring columns beforehand?

Here we create a "source" DataTable with 3 columns, and select two of those columns for the new DataTable:
DataTable srcDataTable = new DataTable();
srcDataTable.Columns.Add("Column A", typeof(string));
srcDataTable.Columns.Add("Column B", typeof(int));
srcDataTable.Columns.Add("Column C", typeof(int));
DataTable dstDataTable = new DataTable();
var desiredColumns = new[] { "Column A", "Column C" };
foreach (DataColumn col in srcDataTable.Columns)
{
if (desiredColumns.Contains(col.ColumnName))
{
dstDataTable.Columns.Add(col.ColumnName, col.DataType, col.Expression);
}
}
Now you can simply loop through the source table and copy the row data as you need it. Example for copying the rows:
foreach (DataRow srcRow in srcDataTable.Rows)
{
var newRow = dstDataTable.NewRow();
foreach (var columnName in desiredColumns)
{
newRow[columnName] = srcRow[columnName];
}
dstDataTable.Rows.Add(newRow);
}
Alternative approach using column numbers:
DataTable srcDataTable = new DataTable();
srcDataTable.Columns.Add("Column A", typeof(string));
srcDataTable.Columns.Add("Column B", typeof(int));
srcDataTable.Columns.Add("Column C", typeof(int));
DataTable dstDataTable = new DataTable();
var desiredColumns = new int[] { 0, 2 };
Dictionary<int, int> columnMap = new Dictionary<int, int>();
for (int colNum = 0; colNum < desiredColumns.Length; ++colNum)
{
columnMap[colNum] = desiredColumns[colNum];
dstDataTable.Columns.Add(srcDataTable.Columns[desiredColumns[colNum]].ColumnName, srcDataTable.Columns[desiredColumns[colNum]].DataType, srcDataTable.Columns[desiredColumns[colNum]].Expression);
}
foreach (DataRow srcRow in srcDataTable.Rows)
{
var newRow = dstDataTable.NewRow();
for (int colNum = 0; colNum < desiredColumns.Length; ++colNum)
{
newRow[colNum] = srcRow[columnMap[colNum]];
}
dstDataTable.Rows.Add(newRow);
}

This line dt3 = new System.Data.DataTable(); creates a new DataTable. But this table doesn't contain any columns yet. In fact, it's an empty table.
This line destRow[0] = sourceRow[2]; tries to set the value of the first column of your table. However, your table doesn't contain any columns yet. And this is what the error message is trying to tell you.
You have to create your column after creating the table. You can do it like this:
DataColumn idColumn = new DataColumn();
idColumn.DataType = System.Type.GetType("System.Int32");
idColumn.ColumnName = "id";
dt3.Columns.Add(idColumn);
Only after this, you will be able to put data into your first column.
Please take a look at this example in the Microsoft docs

What am I doing wrong?
Table dt3 has no column 0, because you haven't added one
Is there any way around it without declaring columns beforehand?
Even though you don't necessarily know the column name or type of dt2's column 2 at compile time, you seem to know that you definitely want column 2 from dt2 to be column 0 of dt3, so make sure you add a column to dt3 that is the same type (and giving it the same name seems reasonable too) as column 2 of dt2:
dt3 = new System.Data.DataTable();
dt3.Columns.Add(dt2.Columns[2].ColumnName, dt2.Columns[2].DataType);
foreach (DataRow sourceRow in dt2.Rows) {
DataRow destRow = dt3.NewRow();
destRow[0] = sourceRow[2];
dt3.Rows.Add(destRow);
}

You can try to use Clone() method to copy structure/columns from source table to destination table:
var dt3 = dt2.Clone();
From the docs.

How to display specific row of data based on a column value

From this code I am trying to only display data rows that contain the fields "DBY" in the Station_From_Code column and "MAT" in the Station_To_Column. This will then be printed onto a HTML page. These fields are definitely in the datatable but when I run this cod the table is empty. I am not used to working with data tables in C# so apologies for the poor coding.
dynamic schedluedContent = JsonConvert.DeserializeObject(scheduledJson);
JArray items2 = new JArray();
foreach (JObject stops in schedluedContent.stops)
{
DataTable dt = new DataTable();
DataRow dr;
dr = dt.NewRow();
dr["From_Station_Code"] = stops["station_code"];
dr["To_Station_Code"] = stops["station_code"];
dt.Rows.Add(dr);
DataRow[] result = dt.Select("From_Station_Code = 'DBY' AND To_Station_Code = 'MAT'");
dt.Rows.Add(result);
GridViewTrainTimes.DataSource = dt;
GridViewTrainTimes.DataBind();
}

It's a long time I have not seen this style of code for working with database tables! EntityFramework comes to change and surely ease the way of working with database and prevent different risks of using SQL commands inside the code.
If you use EF, your code will become something like bellow:
var rows = myDBContext.MyTable.Where(x=>x.From_Station_Code == "DBY" && x.To_Station_Code == "MAT");
GridViewTrainTimes.DataSource = rows;

You can use find match rows and add in new datatable, that contains only your match rows data then you can bind this dt to gridview.
DataTable dt = new Datatable(); // Lets this datatable have data;
Datatable dt2 = new Datatable(); // Copy all matching rows
foreach (DataRow dr in dt.Rows)
{
if (dr["From_Station_Code"].ToString() == "DBY" && dr["To_Station_Code"].ToString() == "MAT")
{
dt2.Rows.Add(dr);
}
}
GridViewTrainTimes.DataSource = dt;
GridViewTrainTimes.DataBind();

How do I search data in from datatable based on user input

I have created one datatable:
DataTable dt=new DataTable();
dt.Columns.Add("Country", typeof(string))
dt.Columns.Add("place", typeof(string))
dt.Columns.Add("Price", typeof(string))
dt.Columns.Add("Desc", typeof(string))
and I have inserted some data in this datatable:
DataRow dtrow = dt.NewRow(); // Create New Row
dtrow["Country"] = "India"; //Bind Data to Columns
dtrow["place"] = "wizag";
dtrow["Price"] = "7520";
dtrow["Desc"] = "Anywhere";
dt.Rows.Add(dtrow);
dtrow = dt.NewRow(); // Create New Row
dtrow["Country"] = "India"; //Bind Data to Columns
dtrow["place"] = "Goa";
dtrow["price"] = "4500";
dtrow["Desc"] = "Anything";
dt.Rows.Add(dtrow);
I have bind this datatable with my grid view. I have also added one textbox and one search button in mmy aspx page. My requirement is that I want to search data based on user input e.g like 4500 or wizag, and if country name is the same I want to show it in one row
How can I do this?

I would use a DataView in this case
DataView dv = new DataView(dt);
dv.RowFilter = "price = 4500 AND Country = 'India'";
GridView.DataSource = dv.ToTable();
GridView.DataBind();

How to add rows to GridView in asp.net c# application

I've already searched many articles on this page and couldn not find the answer that would fit me.
Ok i have two projects (one is server(host) and one is client). The first one is ASP.NET Empty Web Application and the second one is ASP.NET Web Forms site.
In my host i have code for displaying users from my Entity FrameWork database. And in my client i have a form (atleast im trying to create one) where i should be able to display data (users).
Code for displaying data works fine because i've already used it before.
But somehow i cannot create a code for Gridview, which would put data from database into my cells
Lets say ID column would display user ID...Name column would display user name...
I've already set up service reference.
This is a code i've written so far, but it's giving me a few errors.
GridView1.DataSource = null;
GridView1.Refresh();
ServiceReference1.mojWebServiceSoapClient client = new ServiceReference1.mojWebServiceSoapClient();
var userList = client.getUsers();
foreach (var user in userList)
{
DataTable dt = new DataTable();
DataColumn column = new DataColumn();
if (dt.Columns.Count == 0)
{
dt.Columns.Add("ID", typeof(Int32));
dt.Columns.Add("Name", typeof(string));
dt.Columns.Add("Last Name", typeof(string));
}
DataRow row = dt.NewRow();
row[0] = user.userID.ToString();
row[1] = user.Name;
row[2] = user.lName;
dt.Rows.Add(row);
GridView1.DataSource = dt;
GridView1.DataBind();
}
Can you guys please help me fix this? I would really appreciate any input.
Btw this code works, but it only displays 1 user, instead of all (5)

You repeat binding in a for loop and it is incorrect in your case. You should first create a DataTable and next in a for loop add users to it. So the following should satisfy your nedd:
GridView1.DataSource = null;
GridView1.Refresh();
ServiceReference1.mojWebServiceSoapClient client = new ServiceReference1.mojWebServiceSoapClient();
var userList = client.getUsers();
DataTable dt = new DataTable();
DataColumn column = new DataColumn();
dt.Columns.Add("ID", typeof(Int32));
dt.Columns.Add("Name", typeof(string));
dt.Columns.Add("Last Name", typeof(string));
foreach (var user in userList)
{
DataRow row = dt.NewRow();
row[0] = user.userID.ToString();
row[1] = user.Name;
row[2] = user.lName;
dt.Rows.Add(row);
}
GridView1.DataSource = dt;
GridView1.DataBind();
Hope that helped

Change the Column Name in Datatable in C#

I trying to change the column name of the DataTable but some how I lost the data.
foreach (DataRow dr in item)
Ds.Tables[0].ImportRow(dr);
Table.Columns[0].ColumnName = "Barcode";
Table.Columns[1].ColumnName = "Description";
Table.Columns[2].ColumnName = "Price";
Table.Columns[3].ColumnName = "Cost";
Table.Columns[4].ColumnName = "Stock";
Table.Columns[5].ColumnName = "Dept #";
updateDgv.DataSource = Table;

First, the correct code is:
DataTable table = new DataTable();
table.Columns.Add("ItemNo", typeof(string));
table.Columns[0].ColumnName = "Item #";
After your code runs, you have a DataTable with one column named Item #.
There are no rows or data because you didn't add any data. So you didn't lose anything.

I have tested your code and it seems to work fine:
DataTable table = new DataTable();
table.Columns.Add("ItemNo", typeof(string));
table.Columns.Add("ItemName", typeof(string));
DataRow dr = table.NewRow();
dr[0] = "1";
dr[1] = "Name1";
table.Rows.Add(dr);
dr = table.NewRow();
dr[0] = "1";
dr[1] = "Name1";
table.Rows.Add(dr);
table.Columns[0].ColumnName = "Item #";
Probably you are trying to access data through column name later in the code and that is where it is failing. You will not loose the data by just renaming the column name. (Also its a not a good practice use special characters in table column names)
Check out the following screen shots from data visualizer
Before Column Rename:
After Column Rename: