ADO.Net connection in C#

Sumit Dwivedi

Hi Friends,

After making the ADO.Net connection, when i am trying to fetch the s_name value based on the input from textbox using below query. I am getting object reference null error. Can anybody identify what actually is the flaw in the below code

string @searchValue = txtStudentName.Text;

string sql = "SELECT * FROM Student_Detail where s_name=@searchValue";

No record is coming in sql object.

SqlCommand cmd = new SqlCommand(sql, connection);

5 Replies

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Rojalin Sahoo11y ago
As your s_name is a string value(varchar/nvarchar for DB) there must be single quotes for that search value. So change your command like this

string sql = "SELECT * FROM Student_Detail where s_name=' " + @searchValue + " ' ";
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Sumit Dwivedi11y ago
Hi Ravi, I wrote this code:- string connectionString = "Data Source=.;Initial Catalog=Student;Integrated Security=True"; string sql = "SELECT * FROM Student_Detail where s_name=" + @searchValue; SqlConnection connection = new SqlConnection(connectionString); SqlCommand cmd = new SqlCommand(sql, connection); //conne.Open(); connection.Open(); SqlDataReader dr = cmd.ExecuteReader(); DataTable dt = new DataTable(); dt.Load(dr); //dataDataSource = dt; //GridView1.DataBind(); dataGridView1.DataSource = dt; It is throwing error as invalid column name 'sumit' when i am entering sumit as my search character in textbox. The error is coming just after this line:- SqlDataReader dr = cmd.ExecuteReader();
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Krishna Rajput Singh11y ago
Hello Sumit Dwivedi Thanks for writing i hope below links helpful for you...:)

https://msdn.microsoft.com/en-us/library/dw70f090(v=vs.110).aspx

http://csharp.net-informations.com/data-providers/csharp-sql-server-connection.htm

http://www.codeproject.com/Articles/8477/Using-ADO-NET-for-beginners

Special Thanks http://www.c-sharpcorner.com/
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Upendra Pratap Shahi11y ago
use this-

string sql = "SELECT * FROM Student_Detail where s_name="+@searchValue;
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Ravi Patel11y ago
Hi Sumit ,

try this
string @searchValue = txtStudentName.Text;

string sql = "SELECT * FROM Student_Detail where s_name=@searchValue";

SqlDataReader myReader = null;

SqlCommand cmd = new SqlCommand(sql, connection);
cmd.Parameters.Add(searchValue);
myReader = cmd.ExecuteReader();
while(myReader.Read())
{
var id =myReader["Column1"].ToString();

}

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