Following is code:
string checkuser = "select * from [User] where UserName='" + txtusername.Text + "'";
SqlCommand com = new SqlCommand(checkuser, con);
int temp = Convert.ToInt32(com.ExecuteScalar().ToString());
con.Close();
if (temp == 1)
Problem:
whenever i run following code it gives error that Input string was not in a correct format.
try with
string checkuser = "select count(*) from [User] where UserName=@UserName";
your problem is ExecuteScalar return the first row , first column value of the result and it can't convert to a integer
if you have number column , for example age, do as below
string checkuser = "select age from [User] where UserName=@UserName";
your SQL statement widely open for sql injection attacks, you better use parameters
string sql= "select count(*) from [User] where UserName = @UserName";
using(SqlConnection con = new SqlConnection(conString))
using(SqlCommand cmd= new SqlCommand(sql, con))
{
con.Open();
cmd.Parameters.AddWithValue("@UserName", txtusername.Text);
int temp = Convert.ToInt32(cmd.ExecuteScalar().ToString());
if(temp == 1)
{}
}
ExecuteScalar returns first column of the first row the result of your query. And looks like your com.ExecuteScalar().ToString() is not a valid integer, that's why you get this error.
If you want to count your query, you need to use SELECT COUNT(*) instead of SELECT *
And please use parameterized queries. This kind of string concatenations are open for SQL Injection attacks.
Also use using statement to dispose your SqlConnection and SqlCommand like;
using(SqlConnection con = new SqlConnection(strConnString))
using(SqlCommand com = con.CreateCommand())
{
string checkuser = "select COUNT(*) from [User] where UserName = @user";
com.CommandText = checkuser;
com.Parameters.AddWithValue("@user", txtusername.Text);
int temp = (int)com.ExecuteScalar();
if(temp == 1)
///
}
Also you can use ExecuteScalar for getting first row of the specific column value with specifiying column in your query like SELECT columnname from [User]...
You should return a scalar value. But, in your query you are returning a result set which is not compatible with String type.
So, modify your query as follows:
string checkuser = "select count(*) from [User] where UserName='" + txtusername.Text + "'";
The above returns only a single value that can fit into string.
