i want to campare data of sql column F_Name from textbox1.text and if in texbox1 3 charater that match in F_Name(in fast three charter) match then show data in grid view

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C#

private void textBox1_KeyUp(object sender, KeyEventArgs e)
       {
           len = Convert.ToInt32(textBox1.Text.Length);
           string str = "select SUBSTRING(F_Name,1,len) from Opd_Detail where F_name like'" + textBox1.Text + "'";
           textBox2.Text = str;
           c.con_open();
           SqlDataAdapter sda = new SqlDataAdapter(str, Con_Class.con);
           DataTable dt = new DataTable();
           sda.Fill(dt);
           dataGridView1.DataSource = dt;
           c.con_close();
       }

(error is tail in len)

Posted 14-Nov-13 1:11am

Member 10285938

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OriginalGriff · Answer 1 · 2013-11-14T01:27:00

Well, yes. It would be:

C#

len = Convert.ToInt32(textBox1.Text.Length);
 string str = "select SUBSTRING(F_Name,1,len) from Opd_Detail where F_name like'" + textBox1.Text + "'";

len in your SQL statement is part of a string, so the characters 'l', 'e', and 'n' are passed to SQL, not the value of the len variable in the line above.
There are two ways to fix it:
1) Add the value instead of the name:

C#

len = Convert.ToInt32(textBox1.Text.Length);
 string str = "select SUBSTRING(F_Name,1," + len + ") from Opd_Detail where F_name like'" + textBox1.Text + "'";

But that's a bad idea - it's inefficient, and very dangerous.
2) Add it as a parameter to your SQL query - and at the same time protect your database! Do not concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead:

C#

string str = "SELECT SUBSTRING(F_Name,1,@LEN) FROM Opd_Detail FROM F_name like '%' + @COMP + '%'";
System.Data.SqlClient.SqlDataAdapter sda = new System.Data.SqlClient.SqlDataAdapter(str, Con_Class.con);
sda.SelectCommand.Parameters.AddWithValue("@LEN", textBox1.Text.Length);
sda.SelectCommand.Parameters.AddWithValue("@COMP", textBox1.Text);

You do realize that LIKE is a wild card match that only does anything useful if you include wildcards? (Which for SQL is a percent character)

[edit]Typos.[/edit]