SqlBulkCopy - The given value of type String from the data source cannot be converted to type money of the specified target column

For the people stumbling across this question and getting a similar error message in regards to an nvarchar instead of money:

The given value of type String from the data source cannot be converted to type nvarchar of the specified target column.

This could be caused by a too-short column.

For example, if your column is defined as nvarchar(20) and you have a 40 character string, you may get this error.

Source

Please use SqlBulkCopyColumnMapping.

Example:

private void SaveFileToDatabase(string filePath)
{
    string strConnection = System.Configuration.ConfigurationManager.ConnectionStrings["MHMRA_TexMedEvsConnectionString"].ConnectionString.ToString();

    String excelConnString = String.Format("Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=\"Excel 12.0\"", filePath);
    //Create Connection to Excel work book 
    using (OleDbConnection excelConnection = new OleDbConnection(excelConnString))
    {
        //Create OleDbCommand to fetch data from Excel 
        using (OleDbCommand cmd = new OleDbCommand("Select * from [Crosswalk$]", excelConnection))
        {
            excelConnection.Open();
            using (OleDbDataReader dReader = cmd.ExecuteReader())
            {
                using (SqlBulkCopy sqlBulk = new SqlBulkCopy(strConnection))
                {
                    //Give your Destination table name 
                    sqlBulk.DestinationTableName = "PaySrcCrosswalk";

                    // this is a simpler alternative to explicit column mappings, if the column names are the same on both sides and data types match
                    foreach(DataColumn column in dt.Columns) {
                         s.ColumnMappings.Add(new SqlBulkCopyColumnMapping(column.ColumnName, column.ColumnName));
                     }
                   
                    sqlBulk.WriteToServer(dReader);
                }
            }
        }
    }
}  

Since I don't believe "Please use..." plus some random code that is unrelated to the question is a good answer, but I do believe the spirit was correct, I decided to answer this correctly.

When you are using Sql Bulk Copy, it attempts to align your input data directly with the data on the server. So, it takes the Server Table and performs a SQL statement similar to this:

INSERT INTO [schema].[table] (col1, col2, col3) VALUES

Therefore, if you give it Columns 1, 3, and 2, EVEN THOUGH your names may match (e.g.: col1, col3, col2). It will insert like so:

INSERT INTO [schema].[table] (col1, col2, col3) VALUES
                          ('col1', 'col3', 'col2')

It would be extra work and overhead for the Sql Bulk Insert to have to determine a Column Mapping. So it instead allows you to choose... Either ensure your Code and your SQL Table columns are in the same order, or explicitly state to align by Column Name.

Therefore, if your issue is mis-alignment of the columns, which is probably the majority of the cause of this error, this answer is for you.

TLDR

using System.Data;
//...
myDataTable.Columns.Cast<DataColumn>().ToList().ForEach(x => 
    bulkCopy.ColumnMappings.Add(new SqlBulkCopyColumnMapping(x.ColumnName, x.ColumnName)));

This will take your existing DataTable, which you are attempt to insert into your created BulkCopy object, and it will just explicitly map name to name. Of course if, for some reason, you decided to name your DataTable Columns differently than your SQL Server Columns... that's on you.