CODEWITHSUNDEEP
c#dataset
Salik
Salik

Reputation: 518

Adding columns to dataset in c#

I am trying to execute the following code: 

    static DataSet ds_input;
    static DataSet ds_output;


    ds_output.Tables.Add(new DataTable() );
    ds_output.Tables[0].Columns.Add("column_1", typeof(string));
    ds_output.Tables[0].Columns.Add("column_2", typeof(string));
    ds_output.Tables[0].Columns.Add("column_4", typeof(string));
    ds_output.Tables[0].Columns.Add("column_3", typeof(string));

Seems simple to me but somehow it is giving me following errors:

When initializing a new instance in Add(new DataTable()):

Method must have a return type.

When adding columns to ds_output.Tables[0]:

Invalid token '.' in class, struct, or interface member declaration

Update #1:

I had written the above code in the beginning of the class as follows:

namespace Bulk_Verification
{ 
    public partial class Form1 : Form

    {   static DataSet ds_input;
        static DataSet ds_output;
            //ds_output.Tables.Add(new DataTable());
            ds_output.Tables[0].Columns.Add("column_1", typeof(string));
            ds_output.Tables[0].Columns.Add("column_2", typeof(string));
            ds_output.Tables[0].Columns.Add("column_4", typeof(string));
            ds_output.Tables[0].Columns.Add("column_3", typeof(string));

After suspecting that this might be the problem, i shifted these lines just before they are supposed to be used:

public static DataSet verify(DataSet ds_input)
        {
            ds_output.Tables.Add(new DataTable());
            ds_output.Tables[0].Columns.Add("column_1", typeof(string));
            ds_output.Tables[0].Columns.Add("column_2", typeof(string));
            ds_output.Tables[0].Columns.Add("column_4", typeof(string));
            ds_output.Tables[0].Columns.Add("column_3", typeof(string));

This is also the only method that returns a value (a customized dataset i am trying to create). Having the postion changed, now i get the following compiler error when i run the application using debugger, on ds_output.Tables.Add(new DataTable());:

Object reference not set to an instance of an object.

Upvotes: 3

Views: 45646

Answers (2)

Dilip Kumar Choudhary
Dilip Kumar Choudhary

Reputation: 469

Add Column and Update that column of DataSet based on condition in Asp.net C#

//Add new column in DataSet//
dsDetails.Tables[0].Columns.Add(new DataColumn ("Your_New_columnname")); 

//Iterate through DataSet//
foreach(DataRow dr in dsDetails.Tables[0].Rows) 
{
    //Store Specific column's value in a variable to check the condition//
    string name = dr.["Name"].ToString(); 
    for(int i = 0; i<= dsDetails.Tables[0].Rows.Count - 1; i++)
    {
        //Check if name value is null or empty then add new column in DataSet//
        if(name == "") 
        {
            //Update value in newly created column//
            dsDetails.Tables[0].Rows[d]["Your_New_columnname"] = "New_value Yes";
        }
        else
        {   
            //Update value in newly created column//
            dsDetails.Tables[0].Rows[d]["Your_New_columnname"] = "New_value No";
        }
    }
}

dsDetails is DataSet ID

Upvotes: 1

Sriram Sakthivel
Sriram Sakthivel

Reputation: 73502

I assume that you have the code as it is posted. So compiler complaints Method must have a return type and Invalid token '.' in class, struct, or interface member declaration.

You should create a Method and wrap your code in it, It can be instance method, constructor or static method or static constructor.

static DataSet ds_input = new DataSet();
static DataSet ds_output = new DataSet();

private static void InitializeMyDataSet()
{
    ds_output.Tables.Add(new DataTable() );
    ds_output.Tables[0].Columns.Add("column_1", typeof(string));
    ds_output.Tables[0].Columns.Add("column_2", typeof(string));
    ds_output.Tables[0].Columns.Add("column_4", typeof(string));
    ds_output.Tables[0].Columns.Add("column_3", typeof(string));
}

Then call InitializeMyDataSet(); where you need.

Hope this helps.

Upvotes: 5

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