To select Value From Datatable

Question

In the below code I have a datatable I want to select a value from datatable and to check whether value exists or not, but it throws error:

The best overloaded method match for System.Data.DataTable.Select(string) has some invalid argument "," cannot convert from bool to string

Please help me to solve the issue.

Student Details = new Student ();

DataSet ds = Details.Marks();

DataTable dt = ds.Tables[0];

if (dt.Select("RollNo =" != txtRgNo.Text.ToString()) || 
    dt.Select("Name=" != txtName.Text.ToString()))
{
}
else
{
}

user2064325 · Answer 1 · 2015-07-08T12:06:44.097

1

Student Details = new Student ();
DataSet ds = Details.Marks();

DataTable dt = ds.Tables[0];

DataRow dr1=dt.Select("RollNo!= " + txtRgNo.Text.ToString());
DataRow dr2=dt.Select("Name !="+  txtName.Text.ToString())
if (dr1.Length>0 ||dr2.Length>0 )
{
}
else
{
}

edited Jul 08 '15 at 12:06

answered Jul 08 '15 at 07:52

user2064325

21
3

it is throws error The best overloaded method match for System.Data.DataTable.Select(string) has some invalid argument "," cannot convert from bool to string – MVS E Jul 08 '15 at 08:19
@MVSE Missed string concatenation – user2064325 Jul 08 '15 at 08:27

Joel Legaspi Enriquez · Accepted Answer · 2015-07-08T07:55:18.660

0

The DataTable's "Select()" method uses a filter expression. As a sample you can use the following to query for specific RollNo, and it returns DataRow array. If DataRow returns more than one elements, then it exists. Otherwise, it does not exist.

        int rollNumber = 1;
        string filterExpression = string.Format("RollNo = {0}", rollNumber);
        DataRow[] rows = dt.Select(filterExpression);
        if (rows != null && rows.Length > 0)
        {
            //Exists
        }
        else
        {
            //Does not exists
        }

A complete filter expression in your case would be like:

string filterExpression = string.Format("RollNo <> {0} AND Name <> '{1}'", txtRgNo.Text.ToString(), txtName.Text.ToString());

Additional reference to use DataTable.Select(): https://msdn.microsoft.com/en-us/library/det4aw50(v=vs.110).aspx

edited Jul 08 '15 at 07:55

answered Jul 08 '15 at 07:41

Joel Legaspi Enriquez

1,236
1
10
14

When i enter a roll no has E2152 it throws error cannot find column E2152 in DataRow line – MVS E Jul 08 '15 at 08:28
Can you post your code? It seems that your query is looking for "E2152". If the RollNo is a string, then it should be: "RollNo <> '{0}'" Take note of the single quote between '{0}'. This means that the value is string not integer. – Joel Legaspi Enriquez Jul 08 '15 at 08:31

score 0 · Answer 3 · answered Jul 08 '15 at 07:43

0

!= should be part of the string filter you are sending to DataTable.Select but it's also not the correct operator to use. See this link.

Your code should be similar to this:

dt.Select("RollNo <> " & txtRgNo.Text.ToString())

answered Jul 08 '15 at 07:43

Saragis

1,782
6
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score 0 · Answer 4 · answered Jul 08 '15 at 08:04

You can use the Linq Queries to select and filter any fields like this:

Student Details = new Student();

DataSet ds = Details.Marks();

DataTable dt = ds.Tables[0];

if (dt.Rows.Count > 0)
{
    var result = from d in dt.AsEnumerable()
                 where d["RollNo"].ToString() == txtRgNo.Text && 
                       d["Name"].ToString() == txtName.Text
                 select new
                 {
                     RollNo = d.Field<int>("RollNo"),
                     Name = d.Field<string>("Name")
                 };

    if (result.Any())
    {
        // results is not empty ...
    }
}

To select Value From Datatable

4 Answers4