How to solve "Microsoft.Data.SqlClient.SqlException: 'Procedure or function 'xxx' expects parameter '@x', which was not supplied.'" error in .Net?

 This error message indicates that you are calling a stored procedure or function in your SQL Server database, and the procedure is expecting a parameter called @x, but it was not supplied when the procedure was called.

To resolve this issue, you need to make sure that you are passing all the required parameters to the stored procedure or function. Here are a few steps to help you resolve this issue:

1. Check the spelling and case of the parameter: Make sure that the spelling and case of the parameter match the definition of the parameter in the stored procedure or function. SQL Server is case-insensitive by default, but it is good practice to make sure that the spelling and case match to avoid errors.

2. Check the data type of the parameter: Make sure that the data type of the parameter matches the definition of the parameter in the stored procedure or function. If the data type does not match, you will get a similar error message.

3. Check that the parameter is being passed correctly: Make sure that you are passing the parameter correctly when calling the stored procedure or function. You can use the SqlParameter class to specify the parameter name and value:

csharp
using (var command = new SqlCommand("xxx", connection))
{
    command.CommandType = CommandType.StoredProcedure;
    command.Parameters.AddWithValue("@x", x);
    // Add any other parameters
    connection.Open();
    command.ExecuteNonQuery();
}

By specifying the parameter explicitly, you can ensure that the correct value is being passed to the stored procedure or function.

Overall, the key is to make sure that all the required parameters are being passed to the stored procedure or function and that they are being passed correctly.