user defined error message

To show user defined error message, You should throw the exception with Your message in parameter. For example, If you call an Method/Function which is only declared and you have not written any code in the body then NotImplementedException Exception will be used. So
you can throw the exception in the body of Method/function like this -->

public int MyFunction()
{
throw new NotImplementedException(" This is exception throwing Example );
}

Now for Checking in Database, You can simply run the query. For example you dont want the same Email address then use this query.

string Email = "select count(*) from studentdata where Email='" + TextBox1.Text + "'";

SqlCommand com = new SqlCommand(Email, con); \\ here con is Sqlconnection class object

int temp=Convert.ToInt32(com.ExecuteScalar().ToString());

Now if there is any email address present in table then the value of temp will be 1 , Otherwise it will be 0. Now you can simply use If-Else
if(temp==1)
{
\\code to add email address

}
else
{

\\your Error Message
}

2 Replies

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Piyush chhabra11y ago
Accepted answer
To show user defined error message, You should throw the exception with Your message in parameter. For example, If you call an Method/Function which is only declared and you have not written any code in the body then NotImplementedException Exception will be used. So
you can throw the exception in the body of Method/function like this -->

public int MyFunction()
{
throw new NotImplementedException(" This is exception throwing Example );
}

Now for Checking in Database, You can simply run the query. For example you dont want the same Email address then use this query.

string Email = "select count(*) from studentdata where Email='" + TextBox1.Text + "'";
SqlCommand com = new SqlCommand(Email, con); \\ here con is Sqlconnection class object
int temp=Convert.ToInt32(com.ExecuteScalar().ToString());

Now if there is any email address present in table then the value of temp will be 1 , Otherwise it will be 0. Now you can simply use If-Else
if(temp==1)
{
\\code to add email address

}
else
{

\\your Error Message
}
Gowtham Rajamanickam11y ago
public int MyFunction() { throw new NotImplementedException(" This is exception throwing Example ); }